The computer red light is not on, can't open the machine
It is broken like this for a data cable
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The computer does not display the troubleshooting method. (No alarm sound) Step 1: First check if the external wiring of the computer is connected, and re-insert each connection to see if the fault is eliminated. Step 2: If the fault persists, then open the main box to check if there is any excess metal in the chassis, or the short circuit caused by the deformation of the motherboard
, smell the burnt smell in the chassis,
motherboard
There is no burned chip, the capacitor around the CPU is damaged. Step 3: If not, then clean the dust on the motherboard and check if the computer is normal. Step 4: If the fault persists, then unplug the Reset line and other switches and indicators on the motherboard, and then use the screwdriver to short-circuit the switch to see if it can be turned on. Step 5: If you can't boot, then use the minimum system method, unplug the data cable of the hard disk, floppy drive, and CD-ROM drive, and then check if the computer can be turned on. If the computer display
has a boot screen, the problem is Among these devices. Then, one or more devices are connected to the computer. When a device is connected, the fault reappears, indicating that the fault is caused by the device, and finally the device is inspected. Step 6: If the fault persists, the fault may be caused by memory, graphic card
, CPU, motherboard, etc. Then use the plug-in method, the exchange method, etc. to check whether the memory, graphic card
, CPU, etc. are normal. If there is a damaged device, replace the damaged device. Step 7: If the memory, graphics card, CPU and other devices are normal, then discharge the BIOS, use the isolation method, place the motherboard outside the chassis, connect the memory, graphics card, CPU, etc. for testing, if the computer can display, then The motherboard is installed into the chassis for testing until the cause of the failure is found. If the fault persists, you need to return the motherboard to the factory for repair. Step 8: The computer is turned on without display but there is an alarm sound. When the computer is turned on, the system BIOS starts POST (power-on self-test). When it detects that a device in the computer has a fatal error, it controls the speaker to make a sound report. error. Therefore, there may be a failure to turn on the display without an alarm sound. If there is no alarm sound when the computer is turned on, you can check the faulty device according to the meaning of the BIOS alarm sound to eliminate the fault. Common fault diagnosis methods for motherboards: The structure of the computer motherboard is relatively complicated, the failure rate is relatively high, and the fault distribution is also scattered. According to the source of the fault, the motherboard fault can be divided into power supply
fault, bus fault, component fault, and so on. The main causes of motherboard failure are as follows. 1. Reasons for components: The quality of the chips and other components on the motherboard is not good, causing the motherboard to age and damage, resulting in motherboard failure. 2, human reasons: when using the computer, freely hot plug hardware or use metal objects to touch various connectors, resulting in motherboard failure. 3, dust, static cause: due to dust or static caused by poor motherboard contact, short circuit or burned the chip on the motherboard, resulting in motherboard failure. Causes of poor contact: Due to corrosion, oxidation, weakened elasticity, pin de-soldering, breakage, etc., the various chips, sockets, and interfaces in the motherboard are in poor contact, which causes the motherboard to malfunction. For the characteristics of the motherboard and the cause of the failure, when the motherboard fails, the diagnosis method of the motherboard failure is as follows. Step 1: First, carefully check the signs of the motherboard's various slots, fans, chips, etc.: whether there is burnt, blown, blistering, board breakage, socket rust, capacitor bursting on the motherboard : Is the BIOS battery powered? If there is obvious damage, carry out targeted repairs. Step 2: If there is no obvious damage on the motherboard, then use a soft brush to clean the dust on the motherboard. After cleaning, check if the motherboard is normal. If it is normal, it is a malfunction caused by dust. Step 3: If the dust is still not normal after cleaning the dust, then use a multimeter to measure whether the power supply voltage of the motherboard is normal (+5V, +12V, +3.3V, etc.). If there is abnormal voltage, check the power supply
and its main board electrical circuit for faults. Step 4: If the motherboard's electrical voltage is normal, then check the motherboard power-on to see if there is any hot chip in the motherboard. If there is a hot chip, first check if there is a signal at the input and output of the hot chip (see waveform). If there is an input signal, there is no output signal, and then check if the heating chip has a clock signal. If so, the chip is damaged and replaced; if there is no clock signal, check the previous stage of the chip along the line connected to the chip until the faulty component is found. Step 5: After finding the faulty component, do not remove it from the motherboard for the time being. You can use the same type of chip to connect it to it, and then turn it on to see if it is normal. If the motherboard failure disappears, the chip is damaged and the chip is replaced. Step 6: If the motherboard is still faulty, then use the tangent and borrowing method to find the short-circuit line. If it is found that some signal lines are short-circuited with the ground line or the +5V voltage line, the line can be cut and then measured to determine whether it is a chip problem or a motherboard board routing problem. Step 7: If the above method does not work, use the comparison method to find a motherboard of the same model to measure the waveform of the corresponding chip pin and its parameters to confirm whether the chip is damaged.